[6.0] Remove app instances in plugins for layout overrides (joomla#44647)

Author: laoneo

plugins/content/vote/src/Extension/Vote.php

@@ -25,16 +25,6 @@
  */
 final class Vote extends CMSPlugin
 {
-    /**
-     * @var    \Joomla\CMS\Application\CMSApplication
-     *
-     * @since  3.7.0
-     *
-     * @deprecated 4.4.0 will be removed in 6.0 as it is there only for layout overrides
-     *             Use getApplication() instead
-     */
-    protected $app;
-
     /**
      * Displays the voting area when viewing an article and the voting section is displayed before the article
      *

plugins/installer/folderinstaller/src/Extension/FolderInstaller.php

@@ -26,15 +26,6 @@
  */
 final class FolderInstaller extends CMSPlugin implements SubscriberInterface
 {
-    /**
-     * Application object.
-     *
-     * @var    \Joomla\CMS\Application\CMSApplication
-     * @since  4.0.0
-     * @deprecated 6.0 Is needed for template overrides, use getApplication instead
-     */
-    protected $app;
-
     /**
      * Returns an array of events this subscriber will listen to.
      *

plugins/installer/packageinstaller/src/Extension/PackageInstaller.php

@@ -26,15 +26,6 @@
  */
 final class PackageInstaller extends CMSPlugin implements SubscriberInterface
 {
-    /**
-     * Application object
-     *
-     * @var    \Joomla\CMS\Application\CMSApplication
-     * @since  4.0.0
-     * @deprecated 6.0 Is needed for template overrides, use getApplication instead
-     */
-    protected $app;
-
     /**
      * Returns an array of events this subscriber will listen to.
      *

plugins/installer/urlinstaller/src/Extension/UrlInstaller.php

@@ -26,15 +26,6 @@
  */
 final class UrlInstaller extends CMSPlugin implements SubscriberInterface
 {
-    /**
-     * Application object.
-     *
-     * @var    \Joomla\CMS\Application\CMSApplication
-     * @since  4.0.0
-     * @deprecated 6.0 Is needed for template overrides, use getApplication instead
-     */
-    protected $app;
-
     /**
      * Returns an array of events this subscriber will listen to.
      *

plugins/installer/webinstaller/src/Extension/WebInstaller.php

@@ -10,7 +10,6 @@
 
 namespace Joomla\Plugin\Installer\Web\Extension;
 
-use Joomla\CMS\Application\CMSApplication;
 use Joomla\CMS\Event\Installer\AddInstallationTabEvent;
 use Joomla\CMS\Form\Rule\UrlRule;
 use Joomla\CMS\Language\Text;
@@ -40,15 +39,6 @@ final class WebInstaller extends CMSPlugin implements SubscriberInterface
      */
     public const REMOTE_URL = 'https://appscdn.joomla.org/webapps/';
 
-    /**
-     * The application object.
-     *
-     * @var    CMSApplication
-     * @since  4.0.0
-     * @deprecated 6.0 Is needed for template overrides, use getApplication instead
-     */
-    protected $app;
-
     /**
      * The URL to install from
      *